Climatic regimes and the recruitment rate of anchoveta, Engraulis ringens, off Peru   总被引：2，自引：0，他引：2  

Sandra M. Cahuin  Luis A. Cubillos  Miguel iquen  Rubn Escribano 《Estuarine, Coastal and Shelf Science》2009,84(4):591-597

The recruitment rate of Peruvian anchoveta, Engraulis ringens, was studied to test the hypothesis that long-term environmental variation (regime shifts) had a significant impact on density-dependent processes governing the anchovy recruitment during the period 1963–2004. On the basis of previous defined regimes and turning points for the Humboldt Current System, we identified two groups of years for increased recruitment of anchoveta (1963–1971 and 1986–2004), and one unfavorable period (1972–1985). A common intercept and significantly different slopes were found when the recruitment rate was plotted as a function of the spawning stock biomass during those groups of years, suggesting that density-dependent effects on recruitment were affected during different climate regimes. The favorable (unfavorable) regime was characterized by higher (lower) zooplankton volumes, and with a higher frequency of colder (warmer) waters. Dome-shaped relationships between recruitment rate, spawning stock biomass and SST, were detected with a Generalized Additive Model for the favorable regime. Thus, recruitment could be explained by non-linear effects of environmental variables. Ultimately, climatic regimes are affecting the density-dependent effects on recruitment of anchoveta and the mechanisms involved may be associated with changes in the carrying capacity of the spawning habitat of anchoveta off Peru, which in turn are related with the effects of cold and warm regimes.  相似文献   

The Effects of Ocean Acidification on Feeding and Contest Behaviour by the Beadlet Anemone <Emphasis Type="Italic">Actinia equina</Emphasis>     

Tess Olivia Bamber  Angus Charles Jackson  Robert Philip Mansfield 《Ocean Science Journal》2018,53(2):215-224

Increasing concentrations of atmospheric carbon dioxide are causing oceanic pH to decline worldwide, a phenomenon termed ocean acidification. Mounting experimental evidence indicates that near-future levels of CO₂ will affect calcareous invertebrates such as corals, molluscs and gastropods, by reducing their scope for calcification. Despite extensive research into ocean acidification in recent years, the effects on non-calcifying anthozoans, such as sea anemones, remain little explored. In Western Europe, intertidal anemones such as Actinia equina are abundant, lower trophic-level organisms that function as important ecosystem engineers. Changes to behaviours of these simple predators could have implications for intertidal assemblages. This investigation identified the effects of reduced seawater pH on feeding and contest behaviour by A. equina. Video footage was recorded for A. equina feeding at current-day seawater (pH 8.1), and the least (pH 7.9) and most (pH 7.6) severe end-of-century predictions. Footage was also taken of contests over ownership of space between anemones exposed to reduced pH and those that were not. No statistically significant differences were identified in feeding duration or various aspects of contest behaviour including initiating, winning, inflating acrorhagi, inflicting acrorhagial peels and contest duration. Multivariate analyses showed no effect of pH on a combination of these variables. This provides contrast with other studies where anemones with symbiotic algae thrive in areas of natural increased acidity. Thus, novel experiments using intraspecific contests and resource-holding potential may prove an effective approach to understand sub-lethal consequences of ocean acidification for A. equina, other sea anemones and more broadly for marine ecosystems.  相似文献   

Layered organization in the coastal ocean: An introduction to planktonic thin layers and the LOCO project     

James M. Sullivan  Margaret A. McManus  Olivia M. Cheriton  Kelly J. Benoit-Bird  Louis Goodman  Zhankun Wang  John P. Ryan  Mark Stacey  D. Van Holliday  Charles Greenlaw  Mark A. Moline  Malcolm McFarland 《Continental Shelf Research》2010,30(1):1-6

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Amino acids of the Murchison meteorite: II. Five carbon acyclic primary β-, γ-, and δ-amino alkanoic acids     

John R Cronin  Sandra Pizzarello  George U Yuen 《Geochimica et cosmochimica acta》1985,49(11):2259-2265

All ten of the possible five-carbon acyclic primary β-, γ-, and δ-amino alkanoic acids (amino position isomers of the valines) have been positively identified in hot-water extracts of the Murchison meteorite using combined gas chromatography-mass spectrometry (GC-MS) and ion exchange chromatography. With the exception of δ-aminovaleric acid, none of these amino acids has been previously reported to occur in meteorites or in any other natural material. The γ-amino acids (4-aminopentanoic acid, 4-aminc-2-meth-ylbutanoic acid, and 4-amino-3-methylbutanoic acid) are present at higher concentrations (about 5 nmol g^?1) than are the β-amino isomers (3-aminopentanoic acid, 3-amino-2-methylbutanoic acid, allo-3-amino-2-methylbutanoic acid, 3-amino-3-methylbutanoic acid, 3-amino-2-ethylpropanoic acid, and 3-amino-2,2-dimethylpropanoic acid) which are present at concentrations of 1–2 nmol g^?1. These amino acids are less abundant in the meteorite than either the corresponding α-amino acids or the four-carbon homologues. Thirty-six amino acids have now been positively identified in the Murchison meteorite, 17 of which are apparently unique to carbonaceous chondrites. The fact that the meteorite contains all possible five-carbon acyclic primary α-, β-, γ-, and δ-amino alkanoic acids is consistent with a synthetic process involving random combination of single-carbon precursors.  相似文献   

Delay coordinates: a sensitive indicator of nonlinear dynamics in single charged particle motion in magnetic reversals     

Sandra C. Chapman  Nicholas W. Watkins 《Annales Geophysicae》1995,13(8):836-842

The delay coordinate technique is examined as an indicator of the regime of particle dynamics for the system of single charged particle motion in magnetic reversals. Examples of numerically integrated trajectories in both static (zero electric field) and time dependent (corresponding nonzero induction electric field) simple models for magnetic reversals are considered. In the static case, the dynamics can in principle be directly classified by constructing Poincaré surfaces of section; here we demonstrate that whilst the Poincaré surface contains the relevant information to classify the dynamics, the corresponding delay coordinate plot can provide a far more sensitive indication of the onset of nonregular behaviour. In the case of nonperiodic time dependence considered here Poincaré plots cannot in general be constructed directly. Nevertheless, delay coordinate plots can still reveal details of the phase space portrait of the system, and here are shown to indicate whether segments of stochastic motion exist in a given trajectory. It is anticipated that the delay coordinate plot technique as realized here will be a valuable tool in characterizing the behaviour in large numbers of trajectories that are evolved in time-dependent systems, thereby giving us insight into the evolution of the distribution function as a whole, either in prescribed fields or in self-consistent numerical simulations.  相似文献   

Regional policy in Costa Rica: The problems of implementation     

Ernst A. Brugger 《Geoforum》1982,13(2):177-192

In most Third World countries regional planning and regional policy is formally well-developed, but in practice is not implemented. In spite of increasing regional disparities, narrow sectoral and centrally decided programmes and projects dominate over territorial and decentralized ones. This article examines theoretically and empirically why, in the case of Costa Rica, the implementation problem is so difficult and which strategic approaches would best suit an effective regional policy.  相似文献   

Dynamic of the freshwater–saltwater interface in a karstic aquifer under extraordinary recharge action: the Merida Yucatan case study     

Oscar Escolero  Luis E. Marin  Eloisa Domínguez-Mariani  Sandra Torres-Onofre 《Environmental Geology》2007,51(5):719-723

A hydraulic analysis of the interface between freshwater–saltwater behavior was done in the Merida Yucatan zone, two machines that constantly register the groundwater levels were installed, and three electric conductivity logs were taken from wells. When comparing the measured results with the ones obtained using theoretical equations developed to calculate the freshwater–saltwater interface position, it was proved that in some cases these equations can be applied, and in others not. Two effects that rule the behavior of karst aquifers in extraordinary conditions were found.  相似文献   

0.99999999 confidence ambiguity resolution with GPS and Galileo     

Christian Tiberius  Thomas Pany  Bernd Eissfeller  Peter Joosten  Sandra Verhagen 《GPS Solutions》2002,6(1-2):96-99

In this short contribution it is demonstrated how integer carrier phase cycle ambiguity resolution will perform in near future, when the US GPS gets modernized and the European Galileo becomes operational. The capability of ambiguity resolution is analyzed in the context of precise differential positioning over short, medium and long distances. Starting from dual-frequency operation with GPS at present, particularly augmenting the number of satellites turns out to have beneficial consequences on the capability of correctly resolving the ambiguities. With a 'double' constellation, on short baselines, the confidence of the integer ambiguity solution increases to a level of 0.99999999 or beyond. Electronic Publication  相似文献   

Complexity in astroplasmas     

Sandra Chapman  Mervyn Freeman  Sean Oughton 《Astronomy& Geophysics》2001,42(2):2.22-2.22

Ideas of complexity theory – including self-organized criticality – are being applied to the study of turbulence and astroplasmas in the solar system. An RAS MIST meeting in London brought together researchers from different disciplines to compare established paradigms with more recent ideas. Sandra Chapman , Mervyn Freeman and Sean Oughton report.  相似文献   

Shellfish as the impetus for embayment management     

Sandra L. Macfarlane 《Estuaries and Coasts》1996,19(2):311-319

Concern about declining stocks of municipally managed shellfish species in Orleans, Massachusetts, led to several shellfish enhancement programs. Projects included bottom and raft culture of hatchery-raised seed, hatchery and upweller techniques, transplants of seed and adult shellfish, and other management options. However, deterioration of water quality and habitat prompted the town to initiate a multifaceted program to address the issues causing environmental degradation. A water-quality task force, appointed to determine solutions to the problems, recommended changes in land-use practices. A drainage remediation program was undertaken at five sites, resulting in the reopening of a viable shellfish area for the first time in 12 yr. Issues concerning nutrient enrichment, groundwater flow and depth, flushing characteristics of the embayments, proliferation of private docks and piers in the public tidelands, effect of barrier beach dynamics including erosion control measures, and the number of users and diversity of their activies employed on the waters themselves will be addressed in current municipal planning initiatives.  相似文献